1. Field of the Invention
The present invention relates to improvements in reciprocating pumps and in particular to improvements in (1) seals used for check valves in such pumps, (2) fittings for suction and discharge ports and (3) retainers for securing the heads of such pumps to the bodies thereof.
2. State of the Art
In the manufacturing of integrated circuit chips, it has been necessary because of cleanliness requirements and the corrosive nature of the chemicals used to employ chemical pumps that are formed from fluoroplastic materials such as polytetrafluoroethylene. All surfaces of the pumps that are wetted by the chemicals being pumped are formed from the fluoroplastic material. It is advantageous to form the body and heads of such pumps from the fluoroplastic material. The surfaces of all flow channels and pumping chambers which are formed in the body and heads will then, of course, be formed of the fluoroplastic material.
However, three major problems as will be identified below have been encountered in making the chemical pumps from fluoroplastic material. The chemicals being pumped are usually maintained at elevated temperatures, and the three problems are all related to the fact that fluoroplastic materials are subject to plastic deformation and creep at elevated temperatures. The problems are caused because parts of the pump made of fluoroplastic material and which are subject to stress of pressure or other forces tend to distort and change slightly in their shape over time.
The first problem involves leakage in check valve seals used in the pumps. When seal areas in the passages of the pumps distort even slightly, the check seals are likely to malfunction and leak. The second problem involves leakage at fittings on the suction and discharge ports of the pumps. Fittings on the suction and discharge ports, which have generally been threaded into corresponding threaded bores in the body of the pump, specifically tapered pipe threads, often fail or leak due to the distortion of the fluoroplastic material in the area of the threaded bores. The third problem involves leakage at the interface of the heads and bodies of such pumps. Seals around the head and body of the pumps tend to malfunction and leak due to the distortion of the fluoroplastic material due to elevated temperature, pressure and forces used in connecting the head of the pump securely to the body of the pump.
3. Objectives
The principal objective of the invention is to provide improvements in chemical pumps that are made of a fluoroplastic material wherein the improvements eliminate or at least greatly reduce the failures as discussed above due to inherent distortion and creep of the fluoroplastic material.
A particular objective of the present invention is to provide an improved floating O-ring seal in the intake and discharge portions of the pump, wherein the floating nature of the O-ring accommodates small changes in the shape of the retainer means used in positioning the O-ring whereby the O-ring is not subject to distortion by the retainer means and the O-ring makes a fluid tight seat with the check valve.
Another objective of the present invention is to provide novel fittings for suction and discharge ports that in addition to accommodating distortion or creep in the body of the pump also allows various types of fittings to be attached to the body of the pump.
A further objective of the present invention is to provide novel improved means for retaining and securing the heads of the pumps to the bodies thereof which obviates malfunction and leaking due to distortion and creed of the material from which the body and the head of the pump are formed.